Sofa



FIG. 1 is a front perspective view of a sofa showing my new design;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a left side elevation view thereof;

FIG. 4 is a right side elevation view thereof;

FIG. 5 is a rear elevation view thereof; and,

FIG. 6 is a top plan view thereof.

The objects shown in dotted lines depict environment and form no part of the claimed design. 

CLAIM The ornamental design for a sofa, as shown and described. 